The proposed research concerns two functionally related areas: (1) Study of changes in cell surface phenomena resulting from viral transformation. These include loss of density-dependent inhibition of growth, increase in agglutinability by plant lectins and reduction in substrate and cell-to-cell adhesivity which may be related to the in vivo metastatic properties of tumors., (2) Structure of the cell membrane and cell surface. This includes relation of various surface recognition sites to integral membrane proteins and elucidation of the factors controlling disposition of binding sites on the cell surface. Using hemocyanin as a morphological tag visible in shadow-cast replicas for the lectin concanavalin A, I have already demonstrated an increase in the mobility of lectin binding sites in the membrane of SV40 transformed 3T3 cells. The relation between lectin binding sites and other surface moieties, such as sialic acid residues which may have an important role in cellular adhesivity, is not yet defined. The proposed research will utilize electron microscopic observation of thin sectioned, shadow-cast and freeze-etched 3T3 and SV3T3 cells to correlate distribution of negative charges (tagged with positively charged colloidal ferritin) with distribution of lectin binding sites (tagged with hemocyanin). The possible association of these surface sites with membrane glycoproteins or "glycophorins" will be explored. The role of membrane-associated adenylate cyclase in the transfer of information from cell exterior to nucleus via cell surface changes modulated by cAMP and the effect of viral transformation on this regulatory system will also be studied.